Limestone may be burned in the field in heaps, with coal, where it is quarried,. or where the lime is to be used, 30 bush els of coal to 100 of limestone are used, the two being interstratified for burning. Flues are dug in the ground, and the heaps or piles may be made of any desired size : their bases are usually 10 to 15 feet wide, and are carried up in somewhat of a gothic arch shape, to a point or ridge, so as to make the height about the same as the base. The quantity of coal used is in the proportion of about one ton of coal to 100 bushels of limestone—if the coal is fine and slaty, a somewhat larger propor tion is used The length of the piles is made to correspond with the quantity of lime desired at one time, say from 20 to 100 feet in length. The ground flues, which are about 12 or 18 inches square, are extended to about 3 feet out on each side, to admit the wood which is burned in them to start the fire and ignite the coal in the heap, which usually takes 4 to 6 hours, and about half a cord dry wood to 1000 bushels of coal. After the pile is constructed it is plastered over to within about 18 inches of the top on each side, with wet plaster mortar made of clay ; this covering is from 8 to 5 inches thick. About 1# feet of the top heap is construct ed of small stones or stone chips, and is left uncovered until the fire is fully start ed, then covered over with dry dirt to keep down a too rapid combustion. The clay coat is put on before firing, and is kept plastered over close during the burn ing. The outside courses of stone are set on edge in an oblique manner, the direc tion of their inclination being changed each course, which form a zigzag appear ance. The outside courses are laid with care, taking stone of about the same size, but the interior, after the first 2 or 3 courses, is filled up with stone of all sizes, to the extent of 80 pounds, but each coat of coarse stone is filled up and levelled over with small stone of more uniform size—say as large as the first, and then the course of coal is strewn over the smaller stones before another course is added. The first three courses are of about a uniform size of half a brick, and covered with a larger proportion of coal than the courses higher up, the depth or thickness of which is progressively in creased to 15 or 18 inches in the boay of the piles. As the courses are made thicker, so are stone used of larger size— but the coarse stone are to be levelled up and covered with smaller stone to receive the strata of coal.
The ground flues are covered with stone, which are large enough to reach across and lap 4 to 6 inches on each side of the ditch, or the stone may be project ed from either side to meet in the middle of the flue—having sufficient hearing on each side of the flue or ditch to keep them from tilting into the flue when laid. Over these stone, and throughout the whole base of the pile, is laid a cover ing, say 3 or 4 inches thick, of dry wood, and on this is about 2 inches in depth of mineral coal spread over, then a course of limestone, say size of half a common brick. Coal and limestone are thus alter nated for two or three courses, then the thickness of each course is gradually in creased as we raise in height.
In some places, where coal is scarce; wood or peat is used, and these are to be placed in layers, alternate with the lime, in a conical or egg-shaped form, covered with clay, and 5 or 6 yards in diameter, with a funnel of dry brushwood down the centre, two feet wide. The pile is
fired from the top of this funnel, which will burn down to the bottom, and set the whole in combustion.
The best form of the kiln is the egg shape, and wood is preferred to coal in the A lime-kiln should always be built high, and the diameter accord ing to the height. By burning chalk in a kihi, good lime is the result. After lime stone is burned, it is much lighter than before, but it recovers its weight in 4 great measure when exposed to the air, as it absorbs carbonic acid therefrom. The burning of lime is any thing but an agreeable or healthy business, but like many others it is very useful and no. cessary.
There is one thing curious about lime stone, viz., if it be imperfectly burned in the first instance, and the stone cooled, no subsequent burning will make it into quicklime. In agriculture, lime is a great fertilizer, by hastening the decomposition of vegetable matter; and as all marl is a species of lime, it would be the better for being burned before it is used, if the object of adding be to hasten that decomposition. Quicklime is employed in a multitude of preparations subservient to the arts ; for clarifying the juice of the sugar-cane and the beetroot; for purifying coal gas ; for rendering the potash and soda of corn inere,e caustic in the soap manufacture, and in the bleaching of linen and cotton ; for purifying animal matters before dis solving out their gelatine ; for clearing hides of their hair in tanneries ; for ex tracting the pure volatile alkali from mu riate or sulphate of ammonia ; for ren dering confined portions of air very dry ; for stopping the leakage of stone reser voirs, when mixed with clay and thrown into the water ; for making a powerful lute with white of egg or serum of blood ; for preparing, a depilatory pommade with sulphuret of arsenic, &c. Lime water is used in medicine, and quicklime is of general use in chemical researches. Next to agriculture the most extensive applica tion of quicklime is to MORTAR-CEMENTS, which see.
In the employment of lime in agri culture much empiricism has been used, and ground has been as much injured as benefited by its use. The majority of cultivated crops require lime, and it is found in their ashes when burned : hence if the soil do not contain lime these plants cannot grow. If the soil be deficient in lime or only present in small quantity, lime is serviceable ; if it be very clayey lime is also desired. If much vegetable matter be present lime is necessary to make it pass through the decompositions useful for plants that is to form carbonic acid. This is the main use of lime : if there be a small amount of organic matter present, lime will be injurious and the ground will become poorer ; the addition of lime should always be in proportion to the quantity of organic matter present. Lime is more used in England than on this continent, and appears to be more required, it contributing to warm the soil and force the plant, processes performed by a less obscured sun here. Wheat scarcely grows well on English land, which does not contain 2i: per cent. of lime as carbonate, while some of the richest land of the Genesee Valley con tains less than one-half per cent. An ordinary dressing of caustic lime varies from 80 to 100 bushels. Marls may be laid on much heavier.